The present invention relates to a personal authentication device using a living body, particularly relates to a technology of authenticating a person by utilizing a blood vessel pattern which is obtained by taking an image of light that transmits through a living body.
In recent years, importance is set on security concerning personal information. Attention is attracted on biometric authentication as a personal authentication technology ensuring security. The biometric authentication is a technology of executing authentication by using living body information of a human being, and is excellent in availability and secrecy.
There is known authentication using the fingerprint, the iris, voice, face, a vein of the back of the hand, or a vein of the finger as biometric authentication technologies of background arts. Among them, the biometric authentication using the vein is excellent in forgery resistance since internal information of a living body is used.
In the following, a description will particularly be given of a personal authentication device using the vein of the finger. When personal authentication is carried by using a finger vein authentication device, first, a user presents the finger on the authentication device. The finger vein authentication device irradiates the finger with an infrared ray. The infrared ray is scattered at inside of the finger, thereafter, transmitted to outside. Then, the finger vein authentication device takes an image of the infrared ray that is transmitted to a palm side of the finger. At this occasion, hemoglobin in blood absorbs the infrared ray more than a surrounding tissue. Therefore, the light transmitted to the palm side finger has a contrasting difference between weak light which is attenuated by passing through the vein part, and strong light which gets away from a part without vein and is not attenuated. Therefore, an image taken by the finger vein authentication device visualizes the blood vessel (finger vein) which is distributed below the skin on the palm side of the finger as a dark shadow pattern (finger vein pattern). The finger vein authentication device carries out personal authentication by previously registering a characteristic of the finger vein pattern, and calculating a correlation between the finger vein pattern of a user presented in authentication and a previously registered characteristic.
As a background art of a finger vein authentication device of this kind, for example, Japanese Unexamined Patent Application Publication No. 2002-083298 describes a method of correcting a position of a finger or correcting rotation thereof by extracting a contour position of the finger for realizing a highly accurate authentication device. Japanese Unexamined Patent Application Publication No. 2009-289287 describes a method of installing a rod-like marking in a device and measuring an area of concealing a marker by a finger for calculating a thickness of the finger. Japanese Unexamined Patent Application Publication No. 2008-065570 describes that a position of a finger is calculated by installing cameras at a bottom face and a side face of the finger and using images taken from different positions. Japanese Unexamined Patent Application Publication No. 2008-036058 describes an example of using a microlens array for thinning an authentication device.